Measurement methods acetaldehyde

Enzymatic methods have also been employed for measurement of acetaldehyde levels. The affinity of these enzymes for other aldehydes has not been completely determined (13, 38-40), therefore, these methods also suffer from lack of specificity. 

The development of a method for simultaneous measurement of acetaldehyde and formaldehyde allowed a study of the metabolism of methylethylnitrosamine (MEN) as well as DMN and DEN (68). Phenobarbital pretreatment induced the hepatic metabolism of all three nitrosamines. The kinetic constants for DMN, DEN, and MEN were determined. DEN had an apparent that was more than 10 times smaller than that of DMN, indicating that DEN was a better substrate for the deethylase than DMN was for demethylase. 

Another and more accurate microwave method makes use of frequency measurements.1 11 16 28 31 Acetaldehyde is an example of the class of molecules to which this method has been applied. Here there are three equivalent potential minima because of the... 

The computation result yield acetaldehyde concentration as function of time. The value of kinetics parameters, ki, ka, k3 were adjusted to minimize the sum of square of error between the predicted and measured concentration using Hooke Jeeve method [3]. 

A method for the determination of formaldehyde in the presence of acetaldehyde was developed by Nicolet and Shinn.88,100 103 After the excess periodate had been destroyed, these workers swept the acetaldehyde (from the neutral reaction mixture) into a sodium bisulfite solution by means of a stream of carbon dioxide. The acetaldehyde was measured by conventional, bisulfite methods, and the residual formaldehyde was precipitated with Dimedon. This procedure was applied to protein hydroly-zates and to terminal deoxy structures of carbohydrates.88,280 ... 

Measurements of Raman spectra should in principle distinguish between hydrated and unhydrated species in solution, but rather concentrated solutions must be used, and little work has yet been done. The measurements of Matsushima (1963) on aqueous acetaldehyde are in qualitative accord with other methods. 

The reactions are accompanied by a considerable volume change, and a dilatometric method was employed by Bell and Higginson (1949), who added acetaldehyde-water mixtures (containing about equal quantities of MeCHO and MeCH(OH)2) to an excess of acetone, and thus measured kj, in presence of a large number of acid catalysts. The direct hydration of acetaldehyde in aqueous buffer solutions is inconveniently fast at room temperatures, but ( (j + A ) was measured dilatometrically at 0°C by Bell and Darwent (1950), who established the existence of general acid-base catalysis. 

New or improved methods are needed to measure local uptake experimentally. Such data can be used to verify the detailed dosage distribution predicted by the models. For example the retrograde catheter and tracheal cannula system used by Com et al. appears promising for transfer-coefficient measurements within segments of the tracheobronchial tree. A similar method was used by Battista and (3oyer to measure the absorption of acetaldehyde vapor in the dog lung. 

The vapor pressures of all tour compounds hove been measured up to the boiling point Christensen and Smith have determined the vapor pressure of acetaldehyde up to I50 C The vapor pressures from (he boiling point up to the critical point have been calculated by the method of Miller. When compared with ihc experimental data on dcetuldchyde. the error averaged. ... 

Jobs has carried out an extensive series of liquid thermal conductivity measurements over a wide range of temperature on a variety ot compounds. Data on butyraldehyde have been cororlaled with temperature Data ut individual temperature point have been compiled for acetaldehyde, pm-pionaldehyde. and hutyru)deh df > The Jain for formaldehyde were estimated by the method of Robbins and Kmgtea... 

An iron-hydroxamic acid method was used by Andronov and Yudina, who measured air concentrations of vinyl acetate in the presence of butyraldehyde, acetaldehyde, and hydrogen chloride (9.). 

An important, but not widely recognized effect in electron transfer chemistry is the phenomenon that the thermochemical stability order of several tautomeric systems can be inverted upon one-electron oxidation. Hitherto, most of the data stem from gas-phase measurements (photoelectron and mass spectrometry data) or from calculations at several levels of theory (Table 2). While the explicit numbers still differ for each method they all agree on the inversion of the stability order for keto/enol, alkine/allene, imine/enamine, nitrile/isonitrile and aldimine/aminocarbene pairs. One-electron reduction, on the other hand, does not necessarily lead to a thermochemical stability inversion, as demonstrated in the case of acetaldehyde 7cthenol [41]. 

A coulometric titration method was introduced for sequential determination of sulfite, thiosulfate and ascorbic acid (1) in solutions containing sulfite-thiosulfate or sulfite-ascorbic acid couples. Formaldehyde or acetaldehyde can be used to mask the sulfite component. Two sequential measurements of coulometric time, one for both components in the mixture and one for the sample solution in which sulfite is masked, can be used to determine the concentrations of sutfite-thiosulfate and sulfite-ascorbic acid couples. The method is linear for 0.5-60 p,M 1 in the presence of 0.44-13 (xM sulfite, with RSD 0.1-4% and current efficiency of ca 98.0%. The method can be used for determination of the presence of sulfite and 1 in real sample matrices such as mineral waters and vitamin C tablets . 

Using the photoionization technique, Matthews and Warneck (j ) measured the appearance potentials of HCO (g) from formaldehyde, formic acid and acetaldehyde as 11.95, 12.79 and 11.79 eV, respectively, whose average yields AjH (CHC0, g, 0 K) - 197.7 1.5 kcal mol", based on the following A H (0 K) data (in units of kcal mol" ) 51.63 for H(g), 9.35 for OH(g), 35.62 for CHg(g), -26.78 for HgCOCg) (2), -88.74 for HCOOH(g) (3) and -37.14 for CHgCHO (4). The appearance potentials obtained from photoionization are several tenths to 1 eV lower than the recent electron impact data (5, 6, 7, 8, 9). The appearance potentials determined by the electron impact method tend to be high because the fundamental nature of the process does not lead to a sharp o pet in contrast to the step-function behavior of photoionization onset. 

As the titration method for the determination of acetaldehyde is very unspecific and measures more than just aldehydes or acetaldehyde, the following specific enzymatic method is recommended. It was introduced in the harmonized monograph of povidone in Ph.Eur., USP and JP. 

Acetaldehyde is stoichiometrically oxidized to acetic acid by nicotinamide-adenine dinucleotide (NAD) in the presence of aldehyde dehydrogenase. This method measures the sum of free and bound acetaldehyde. 

Measurements with pure acetaldehyde with a concentration of 5-55 pg/10 ml demonstrate the linearity of the method with a correlation coefficient of 0.99998. 

To measure ethanol in blood, enzymatic analysis is the method of choice for many laboratories. In this method, ethanol is measured by oxidation to acetaldehyde with NAD, a reaction catalyzed by alcohol dehydrogenase (ADH). With this reaction, formation of NADH, measured at 340nm, is proportional to the amount of ethanol in the specimen. The reaction is driven almost completely to the right by use of excess NAD and ADH and agents such as semicarbazide or tris (hydroxymethyl) aminomethane to trap acetaldehyde as it is formed. ... 

Lauder (1948) also gives data for the rate of hydration of acetaldehyde based on dilatometric and refractometric measurements. He did not realize the catalytic nature of the reaction, and worked in unbuffered solutions which presumably contained small but variable quantities of acetic acid this may account for the erratic nature of his results and for the fact that his rates decrease with increasing temperature. It is more difficult to explain the fact that most of his recorded rates are considerably lower than the minimum (water-catalysed) velocity obtained by other methods. He used concentrated solutions of acetaldehyde, which may have contained considerable quantities of the hemihydrate (MeCH0H)20. The presence of this species has been recently suggested by Ahrens and Strehlow (1965) on the basis of N.M.R. spectra there is evidence for the existence of analogous species in aqueous formaldehyde solutions (Bezzi et al., 1951), and the hemihydrate (CH2CI. CH0H)20 can be isolated as a solid (Natterer, 1882). 

The method used to measure the amount of the copigment complex in a red wine, and the other measures, is referred to as the copigmentation assay. This method measures the absorbance of a sample altered by dilution together with those resulting from additions of acetaldehyde or sulfur dioxide (7, 8). The procedure differs from previous methods in that all readings are made at a standardized pH (3.6) and at 12% ethanol and makes no assumptions about the extinction coefficients, ionization or the color shifts. It also subtracts the color due to copigmentation from wine color in order to make the anthocyanin estimate. 

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